纤维／基体界面裂纹扩展断裂能

本文通过研究纤维／基体界面裂纹断裂能，分析了几种界面脱粘断裂功的理论表达式；着重研究了单纤维拔出试验中界面残余压应力及界面摩擦对界面裂纹能量释放率的重要性．     

一种新的界面脱粘和纤维拔出模型

对纤维增强复合材料中界面的脱粘和纤维的拔出行为进行了研究,通过纤维间距d来考虑纤维之间的相互影响,改变脱粘段的剪切强度和粘结段的临界能量释放率,推导出了纤维拉拔荷载和纤维脱粘长度之间的变化关系,与StangH的模型进行了对比,当纤维间距较大时,纤维之间的相互影响相对较小,此时与StangH的单根纤维拉拔情况较为相符,但当纤维间距较小时,由于临近纤维的影响,使得在相同脱粘长度的情况下,纤维拉拔荷载和纤维拔出端位移有减小的趋势,改变复合材料板层的厚度,由于影响了基体的变形,界面的脱粘和纤维的拔出行为也受到了相应的影响。     

石墨烯与柔性基底界面载荷传递的拉曼光谱实验

本文研究了CVD制备的大尺寸石墨烯与柔性PET基底在拉伸变形过程中切向界面载荷传递的问题,采用原位拉曼光谱实验给出了加载过程中石墨烯的正应变、正应力以及界面切应力的分布曲线。分析表明,石墨烯与PET基底间的载荷传递存在四个阶段,分别是初始阶段、粘附阶段、滑移阶段和界面脱粘破坏阶段。在此基础上,本文对50μm、140μm、270μm和600μm四种尺寸石墨烯试件的界面力学性能进行测量,得到了不同尺寸石墨烯试件的界面力学性能参数,并初步给出了基底变形引起的石墨烯切向界面粘接能的变化,同时分析了试件尺寸对石墨烯界面力学性能的影响。实验结果表明,石墨烯材料和柔性基底最大切应力与临界脱粘切向界面粘接能等界面强度指标受到尺寸的显著影响,尺寸越小切向界面强度越高,反之,尺寸越大则越低。     

固体薄膜/液体膜/基底层状结构中液体膜/基底界面不平整性对结构稳定性影响

考虑液体层较薄的情况下液体膜/基底间界面不平整对结构的稳定性,特别是固体薄膜稳定时的褶皱变形产生的影响。用一扰动函数模拟液体膜/基底间界面的不平整,计算固体膜受力变形前后结构能量的变化,进而分析其稳定性。取两个扰动函数的特例,具体分析了液体膜/基底间界面不平整对结构能量变化以及对结构平衡态的影响。结果表明,平衡时固体膜褶皱变形与原来假设液体膜/基底间界面为理想平整面所得的结果有很大不同。     

陶瓷／金属连接界面韧性及其实验测定

基于能量叠加和梁的等效截面转换原理,本文导出了计算Ｓａｎｄｗｉｃｈ梁试样界面裂纹扩展能量释放率的解析式,并利用专门设计的四点弯曲实验系统测得了Ｓｉ３Ｎ４／Ａｌ真空扩散连接界面的韧性,进而为优化陶瓷／金属连接工艺、筛选材料组配和评价其连接界面的抗断裂性能提供了必要的研究方法和实验手段。     

基于能量释放率的界面断裂实验分析方法

基于对断裂力学常用实验方法的研究,结合界面断裂问题的特殊性,以断裂力学为理论基础,通过能量释放率建立了界面断裂测量的实验分析方法,并且利用文献中的实验数据进行了验证,取得了良好的一致性.该方法通过测量试验件的载荷-位移关系,利用裂纹扩展过程中的能量变化关系得到该裂纹长度下的临界能量释放率;在此基础上,根据试件的阻抗能量曲线预测结构的最大承载能力.该方法以能量释放率为理论基础,为界面裂纹的强度分析提供了合理的手段,基于能量角度建立的实验分析方法也具有良好的实用性和适用性.     

AN EXPERIMENTAL METHOD BASED ON ENERGY RELEASE RATE OF INTERFACIAL FRACTURE

基于对断裂力学常用实验方法的研究,结合界面断裂问题的特殊性,以断裂力学为理论基础,通过能量释放率建立了界面断裂测量的实验分析方法,并且利用文献中的实验数据进行了验证,取得了良好的一致性.该方法通过测量试验件的载荷位移关系,利用裂纹扩展过程中的能量变化关系得到该裂纹长度下的临界能量释放率;在此基础上,根据试件的阻抗能量曲线预测结构的最大承载能力.该方法以能量释放率为理论基础,为界面裂纹的强度分析提供了合理的手段,基于能量角度建立的实验分析方法也具有良好的实用性和适用性.     

弱界面端初始失效位置的试验初探

通过双材料受压试验研究了弱奇异性界面端的界面初始脱粘点的位置问题。实验材料采用钢和有机玻璃,根据弱奇异性要求和界面端应力分布特征,设计、制作了试件,并进行了初始脱粘实验。由实验发现楔形角为30°、45°和55°试件的界面初始脱粘点位置均在界面内部,脱粘是由有限应力引起的。63°是个临界角楔形角,大于63°试件,脱粘多会从界面端开始,即脱粘由奇异的界面应力引起的。此外界面正应力若为拉应力时,它对界面脱粘有很大的贡献。     

界面裂纹非对称扩展模型

提出了一种新的复合材料结构中层间脱层裂纹扩展模型，该模型能够揭示裂纹扩展对裂纹左右尖端能量释放率的相对大小及界面材料性能的依赖性，能够比较真实地揭示复合材料结构层间脱层裂纹扩展复杂性的特点．     

纤维增强陶瓷基复合材料疲劳迟滞回线模型研究

纤维增强陶瓷基复合材料初始加载到疲劳峰值应力时, 基体出现裂纹, 纤维/基体界面发生脱粘. 在疲劳载荷作用下, 纤维相对基体在界面脱粘区往复滑移使得陶瓷基复合材料出现疲劳迟滞现象. 建立了纤维陶瓷基复合材料疲劳迟滞回线细观力学模型, 采用断裂力学方法确定了初始加载纤维/基体界面脱粘长度、卸载界面反向滑移长度与重新加载新界面滑移长度, 分析了4种不同界面滑移情况的疲劳迟滞回线. 假设正交铺设与编织陶瓷基复合材料疲劳迟滞回线主要受0°铺层、轴向纱线内纤维/基体界面滑移的影响, 预测了单向、正交铺设与编织陶瓷基复合材料在不同峰值应力与不同循环的疲劳迟滞回线, 与试验结果吻合.      

Frictional effects of interface bonding energy in blister testing

Blister tests are used to investigate the size effect on the critical energy release rate for the onset of debonding of interfaces between commercial tape and plain steel. The measured data display a size effect if the interfacial friction is not taken into account. A proportional displacement model is thus proposed to simultaneously evaluate the critical energy release rate and the frictional parameter. Theory and experiment give a critical energy release rate of 1.9956 Pa m for the onset of interfacial debonding between the commercial tape and the plain steel and it is independent of the blister size.     

Stress and Moisture Effects on Thin Film Buckling Delamination

Deposition processes control the properties of thin films; they can also introduce high residual stresses, which can be relieved by delamination and fracture. Tungsten films with high 1–2 GPa compressive residual stresses were sputter deposited on top of thin (below 100 nm) copper and diamond-like carbon (DLC) films. Highly stressed films store large amounts of strain energy. When the strain energy release rate exceeds the films' interfacial toughness, delamination occurs. Compressive residual stresses cause film buckling and debonding, forming open channels. Profiles of the buckling delaminations were used to calculate the films' interfacial toughness and then were compared to the adhesion results obtained from the superlayer indentation test. Tests were conducted in both dry and wet environments and a significant drop in film adhesion, up to 100 times was noticed due to the presence of moisture at the film/substrate interface.     

Peeling behavior of a viscoelastic thin-film on a rigid substrate

In order to study the adhesion mechanism of a viscoelastic thin-film on a substrate, peeling experiment of a viscoelastic polyvinylchloride (PVC) thin-film on a rigid substrate (glass) is carried out. The effects of peeling rate, peeling angle, film thickness, surface roughness and the interfacial adhesive on the peel-off force are considered. It is found that both the viscoelastic properties of the film and the interfacial adhesive contribute to the rate-dependent peel-off force. For a fixed peeling rate, the peel-off force decreases with the increasing peeling angle. Increasing film thickness or substrate roughness leads to an increase of the peel-off force. Viscoelastic energy release rate in the present experiment can be further predicted by adopting a recently published theoretical model. It is shown that the energy release rate increases with the increase of peeling rates or peeling angles. The results in the present paper should be helpful for understanding the adhesion mechanism of a viscoelastic thin-film.     

涂层/基体材料界面结合强度测量方法的现状与展望

界面结合强度是涂层/基体材料体系中的一项重要力学性能指标.而表征与评价涂层/基体材料的界面结合强度又得依靠实验 方法的测定.由于涂层/基体材料体系的多样性与复杂性, 至今还没有形成适合于测量这类材料的界面结合强度的标准方法. 目前, 常用来测量涂层/基体材料的界面结合强度的方法有：拉伸法、剪切法、弯曲法、划痕法、压入法等.本文就目前表征 与评价涂层/基体材料界面结合强度的测量方法做了综述, 讨论了它们的适用范围, 比较了它们的优势与不足.     

Quantitative characterization of the interfacial adhesion of Ni thin film on steel substrate: A compression-induced buckling delamination test

A compression-induced buckling delamination test is employed to quantitatively characterize the interfacial adhesion of Ni thin film on steel substrate. It is shown that buckles initiate from edge flaws and surface morphologies exhibit symmetric, half-penny shapes. Taking the elastoplasticity of film and substrate into account, a three-dimensional finite element model for an edge flaw with the finite size is established to simulate the evolution of energy release rates and phase angles in the process of interfacial buckling-driven delamination. The results show that delamination propagates along both the straight side and curved front. The mode II delamination plays a dominant role in the process with a straight side whilst the curved front experiences almost the pure mode I. Based on the results of finite element analysis, a numerical model is developed to evaluate the interfacial energy release rate, which is in the range of 250–315 J/m² with the corresponding phase angle from −41° to −66°. These results are in agreement with the available values determined by other testing methods, which confirms the effectiveness of the numerical model.     

Dynamic fracture mechanics analysis for composite material with material non-homogeneity in thickness direction

The problem considered here is the response of a non-homogeneous composite material containing some cracks subjected to dynamic loading. It is assumed that the composite material is orthotropic and all the material properties depend only on the coordinatey (along the thickness direction). In the analysis, the elastic region is divided into a number of plies of infinite length. The material properties are taken to be constants for each ply. By utilizing the Laplace transform and Fourier transform technique, the general solutions for plies are derived. The singular integral equations of the entire elastic region are obtained and solved by the virtual displacement principle. Attention is focused on the time-dependent full field solutions of stress intensity factor(SIF) and strain energy release rate. As a numerical illustration, the dynamic stress intensity factor of a substrate/functionally graded film structure with two cracks under suddenly applied forces on cracks face are presented for various material non-homogeneity parameters.     

Peeling experiments of ductile thin films along ceramic substrates – Critical assessment of analytical models

Two types of peeling experiments are performed in the present research. One is for the Al film/Al₂O₃ substrate system with an adhesive layer between the film and the substrate. The other one is for the Cu film/Al₂O₃ substrate system without adhesive layer between the film and the substrate, and the Cu films are electroplated onto the Al₂O₃ substrates. For the case with adhesive layer, two kinds of adhesives are selected, which are all the mixtures of epoxy and polyimide with mass ratios 1:1.5 and 1:1, respectively. The relationships between energy release rate, the film thickness and the adhesive layer thickness are measured during the steady-state peeling process. The effects of the adhesive layer on the energy release rate are analyzed. Using the experimental results, several analytical criteria for the steady-state peeling based on the bending model and on the two-dimensional finite element analysis model are critically assessed. Through assessment of analytical models, we find that the cohesive zone criterion based on the beam bend model is suitable for a weak interface strength case and it describes a macroscale fracture process zone case, while the two-dimensional finite element model is effective to both the strong interface and weak interface, and it describes a small-scale fracture process zone case.     

沿厚度非均匀复合材料的动态断裂力学研究

对于非均匀复合材料中多个裂纹的动态断裂力学问题，提出了一种分析方法，假设复合材料为正交各向异性并含有多个垂直于厚度方向的裂纹，材料参数沿厚度方向为变化的，沿该方向将复合划分为许多单层，假设单层材料参数为常数，Ｆｏｕｒｉｅｒ变换法，在Ｌａｐｌａｃｅ域内推导出了控制问题的奇异积分方程组并用虚位移原理求解，然后利用Ｌａｐｌａｃｅ数值反得刺裂纹尖端的动态应力强度因子和能量释放率，作为算例，研究了带有两个裂     

微粒填充流变材料界面开裂的局部临界应力及尺寸效应的理论分析

研究了以等轴粒子填充流变材料的边界开裂机理，采用能量准则导出了以界面能表示的界面开裂局部临界应力的简洁表达式。由于临界应力正比于１√α，从而可以非常方便地研究粒子开裂的尺寸效应，以碳酸钙微粒填充的聚丙烯复合材料为例进行了理论分析，通过比较界面开裂的能量准则和张应力准则得出结论：即使按照保守的方法估算，即在界面强度等于基体强度的条件下，只要粒径不超过０．２微米，若能量准则得到满足，则张应力准则也会得